Roller-skating injuries

An epidemiologic survey of roller-skating injuries in Metroville, a city with a population of 100,000 (during the midpoint of the year), produced the following data for a particular year:

 

Number of skaters in Metroville during any given month

12,000

 

Roller-skating injuries in Metroville

600

 

Total number of residents injured from roller-skating

1,800

 

Total number of deaths from roller-skating

90

 

Total number of deaths from all causes

900

 

The cause-specific mortality rate from roller-skating was:

 

90/600 × 100,000

 

90/100,000 × 100,000

 

90/1,800 × 100,000

 

90/900 × 100,000